Police disclosed the findings Friday. The city medical examiner's office says an autopsy was inconclusive and more tests are needed.
Police believe 17-year-old Tiana Rodriguez gave birth to the baby at a friend's house and that the infant was later asphyxiated.
The remains were discovered Thursday when a security guard stopped Rodriguez and her friend Francis Estevez at a Victoria's Secret store.
Both girls were arrested. It's unclear whether either girl has a lawyer.
A woman who answered the phone at a possible home number for Rodriguez said she knew nothing about the matter. A woman who said she was Estevez's mother hung up after saying she hadn't spoken with her daughter since her arrest.